Conversion algorithm for ERDA multielement spectra and its application to thin-film problems

J. K. Walters
Department of Physics and Astronomy
University College
Gower Street
London WC1E 6BT
UK

M. Kühn, C. Spaeth
Technische Universität Chemnitz-Zwickau
Institut für Physik
D-09107 Chemnitz
Germany

E. Dooryhee
ESRF
B.P. 220
F-38043 Grenoble Cedex 9
France

R. J. Newport
Physics Laboratory
The University, Canterbury
Kent CT2 7NR
UK

The effects of nitrogen incorporation on the atomic-scale structure of amorphous CN_x samples have been studied for 0, 5, 20 and 30 at.% N concentration, by X-ray diffraction. Significant differences in the structure are observed on the incorporation of only 5 at.% N, and the changes in structure continue as further N is added. From the experimental data, we are able to obtain directly the average bond distances and then calculate the average bond angles for each of the samples. The average first neighbour distance shows a gradual decrease from 1.55 Å for 0 at.% N, to 1.44 Å for 30 at.% N, and a similar trend is observed in the position of the second neighbour peak. This gives a corresponding increase in the average bond angle from 108° to 114°. The results show an increase in the fraction of sp² bonded carbon atoms with increasing N concentration, and there is evidence for the presence of significant numbers of CN triple and C=N bonds. These results are also consistent with stress, hardness and optical gap measurements for these samples.